Recently, there has been renewed interest in solar cells as alternative energy sources. To increase the efficiency of solar cells, it is desirable to maximize the active area of a solar cell, i.e., the area of the cell that absorbs light. However, design constraints make it necessary to provide, for example, electrical contacts to allow for the use of the electrical power generated by the cell, or separators between p- and n-doped regions of the cell to avoid rapid charge recombination of electron/hole pairs generated by absorbed light. These design constraints may limit the active area available for light absorption, thereby lowering the actual cell efficiency below the theoretical maximum photon-to-electron conversion efficiency.
Inderdigitated back contacts (IBCs) allow to attach electrical contacts to the back side, i.e., the side facing away from the light source, which avoids shadowing losses that otherwise take place in solar cells with electrical contacts on the front side, i.e., the side facing the light source. Nevertheless, traditional IBC solar cells contain an insulating region as a separator between p- and n-doped regions of the cell to prevent charge recombination. The insulating region, however, reduces the amount of active area for photon absorption, and, consequentially, the efficiency of the solar cell. Moreover, the insulating region, also referred to as spacing or border, between interdigitated contacts must further include a budget for misalignment because contacts defined in different lithography levels may not be in perfect alignment.
Further, solar cell designs utilizing n-doped and p-doped regions that are interdigitated back contacts offer a number of advantages in both solar cell efficiency and ease of processing. IBCs can be advantageous to process in cases where only one side of a quasi-planar absorber layer is accessible for contact formation or in cases where having both contacts on the same side of the absorber layer makes it easier to connect the adjacent solar cells comprising a solar module. It would therefore be extremely desirable to have a method to make interdigitated contacts that allows the contact (or carrier collection) area to be maximized while minimizing the potential for contact misalignment.